Fade To Black
by bethanyyerinn
Summary: My dip into the dark side of BBC Sherlock. Post series 3.
1. Chapter 1

**Disclaimer: I own nothing.**

**Established Johnlock.**

**Rated M for graphic depictions of gore.**

**Usually I give fat long summaries of what to expect in my stories, but not this time. What I've said above is all you get. You're just going to have to read to see what this one's about.**

**But, I should say, if you've read my stuff before and are looking for more light fluffy fun, then press the back button. This isn't what you're looking for.**

**Enjoy. ;D**

* * *

Sherlock groaned loudly in frustration.

Paced around a little.

Stopped and stared at the ceiling.

Then whined, "Johhhhhnnnn!"

John looked up from the telly, exasperated. "Sherlock, would you quit that and sit down?"

"Lestrade hasn't gotten back!"

"Well it's only been ten minutes, now hasn't it? Have a sit."

"John, I need him to phone me."

"And he will when he has the information you asked for. You are aware you asked for the name of every doctor in Sweden, right? That must take time."

Sherlock let out another long bellow of a moan and John rolled his eyes.

"You're a child."

"It's important!"

John looked back up at Sherlock, but this time, with his eyes a bit more focused, looking Sherlock up and down carefully.

"What is it with this case? You're more obsessed than usual."

Sherlock's eyes narrowed so infinitesimally that there was no way John noticed. He hated when John had his occasional moments of keenness, because they were always at times that were the most inconvenient for Sherlock.

He had to sidetrack him. As John's mind was mostly average, it was easy to shove off a scent.

So Sherlock finally sat down, as John had been suggesting, and the detective put his head in the other man's lap.

"Now, that's better," said John, with the grin that Sherlock secretly adored. John's fingers, as they often did, tangled in Sherlock's hair, fingertips massaging his scalp. If Sherlock were capable, he'd probably literally purr every time John did that. No physical contact felt better to him—sex excluded.

But his happiness didn't last long. John apparently would not be distracted tonight. "But really, what's got you so excited about this case? I mean, more than usual."

Sherlock couldn't avoid it a second time. Too suspicious. So he said, careful to sound as bored as usual, "Well, it's certainly different. My mind is getting a work-out for once."

"It's disgusting, is what it is," said John irritably. "This bloke—or woman—"

"A man is statistically more likely," Sherlock interrupted. He loathed repeating himself, and he was sure he'd said that eight years ago. Oh well.

John ignored Sherlock's insertion, continuing. "—was trained to heal people and they're using it for murder." He shook his head. "Who the fuck does something like that?" Luckily, John was now in a silent, righteous rage, so he was done pestering Sherlock.

_Who indeed?_ wondered Sherlock, closing his eyes and feeling John's fingers rubbing against his head, gentle and soothing even in his anger.

John. Sweet John. John would never look at him the same if he knew. Never. He'd think Sherlock was a monster.

And maybe Sherlock himself would agree.

Because why _was_ Sherlock so obsessed with this case?

Because the crimes were flawless and it was simply intoxicating. They were so perfect that Sherlock was most surprised Moriarty wasn't behind them.

After Jim made his public return, he stayed ominously quiet. Then these murders started. Clean. Clinical. No evidence. Missing organs taken out with medical expertise. It had to be Moriarty because nobody else was enough of a genius.

Until Moriarty's body showed up. Every body was missing a different organ. Always the most damaged. The alcoholic was missing their liver, the drug addict their brain, the smoker their lungs. You see the pattern.

And with Moriarty... His heart was missing. It was poetic. It sealed Sherlock's obsession. This killer was an utter genius to get Moriarty under his knife.

And, yes, it could have been a fake body. It wouldn't be the first time. But, somehow, Sherlock knew it wasn't. He'd had a feeling as he was going through being with John again after being away two years, and the wedding, that Moriarty wasn't really dead. It didn't seem possible. Then there he was, on the telly, and he couldn't bring himself to be surprised.

Moriarty didn't do anything really after that. He was biding his time, of course. It was months. The accident happened, and then the funeral: one coffin, two corpses. The sign of three didn't matter after that, because now there was just one. John was a mess. He wasn't alone, because he had Sherlock, but he'd become so accustomed to having Mary, and to the thought of a child… he was truly broken. For ages. It killed Sherlock to watch it.

The last thing John needed was Moriarty to strike again.

But strike he did, about a month later. John had already moved back in with Sherlock by then, so he heard about it the same time Sherlock did.

The first corpse was a blind woman who'd had her eyes removed. Still alive when they were taken, no pain relievers. She had an anti-clotting agent in her blood that caused her to bleed out fairly quickly. Sherlock had been only mildly impressed, until he was on the case for a few months, two more bodies appearing in that time, with nothing at all leading to a killer. Serial killers were hard because you had to wait for a mistake.

But now, more than a year later, there were fifteen bodies piled up and there weren't any mistakes. Not one. It was unheard of.

It was intriguing.

And there it was. Sherlock was afraid of himself as of now because these murders were so perfect, so immaculate that he didn't want to find the killer in order to apprehend him. He wanted to marvel at him. Bow at his feet. Fuck him, if that's what he wanted. Anything. It was perfection and he was dangerously close to being in love with it. He on more than one occasion had gotten hard at the thought of whoever this genius was.

Well, once he figured out it wasn't Moriarty, that is. He was the twelfth body. The one that really got Sherlock going. If this person was clever enough to truly end James Moriarty... Sherlock's heart nearly fluttered at the thought of it.

But it was stupid. It made no sense. He and John had been dating for two months now, and it didn't take Sherlock long to realize dating John was all he really wanted from life, aside from solving cases. So what was he doing fantasizing about a murderer when he had his perfect John right here with him? John who adored him, John who would do anything for him...

Yet in the late hours of the night, as he sat in the dark sitting room long after John went to bed, he'd yearn for something more sinister.

When he slept with John, it was sweet, full of love they were both still too self-conscious to express with words.

But if Sherlock were sleeping with the murderer... A doctor like John, but different in every other way... he wouldn't be so gentle with Sherlock. Would he hit him? Would he enjoy blood-play? Was Sherlock insane for being aroused by that?

He'd considered that maybe he just needed some rougher sex to get rid of these thoughts, but he could never mention BDSM with John when the chance to do so came. He found himself unable to talk with something strangely like nerves stopping his throat.

So now they were sitting on the couch, John playing with Sherlock's hair as he sat with his eyes closed and imagined with only some shame the type of glorious mind that must be behind these pristine murders. And he wondered, not for the first time, if he would be able to turn the man in once he caught him.

He was sure he already knew the answer, and that was what scared him most.


	2. Chapter 2

Even though Sherlock and John both slept in Sherlock's bedroom, John kept his clothes and things up in his own room. Sherlock had never really asked why. To keep some semblance of privacy?

So John went up to his room that morning to get dressed and when he opened the door, Sherlock knew something was wrong from the way he heard him stop in the doorway, not going in any further. He paused for a full five seconds before going deeper into the room. Sherlock then sprang up from his spot on the couch, going up the steps three at a time.

When he got to the doorway, John was standing by the window.

It was an obvious break in. The window was open, the latch was damaged, a vase was tipped over.

In fact, the break in was so obvious that Sherlock was sure it was intentional.

And an intentionally obvious break in at 221B, probably done to attempt to induce fear, could only be the work of one man, Sherlock was sure. He got an electric shock all the way down through his toes thinking about it, about the killer being here, in his flat. So near him.

He knew there was no point in looking for clues, really, but he did anyway.

There was nothing, of course. Internally, he was laughing. He was good. He really was.

Then he looked over at John.

Specifically, at what John was holding.

His breath caught. The killer had come for a purpose.

To drop off a letter.

John was holding it without paying it much mind.

Ah, so the fear tactic didn't work on Sherlock, but it did John. Well, to a point. The bravery of the soldier, after all. A coward John was _not_, but he certainly didn't seem happy. He was mostly staring at the window, maybe looking for clues too. He, at least a little, knew Sherlock's methods. He knew what to look for, he just didn't have the eye.

After being silent for a long while, John spoke. "If he can get in here that easily... What else can he do?"

Yes, if he could break into the flat in the middle of the night whenever he wished, what would he do to them? Would he take Sherlock against the wall and—

He stopped the thought there.

"I wouldn't worry about it, John," he said simply. "It's just a game."

John rolled his eyes at the words, shaking his head in revulsion. "Don't know why he'd kill Moriarty. Seems like the two of them would get on swimmingly."

Sherlock had to use all his self-control not to snap, _He's nothing like Moriarty!_ But John would certainly notice the strangeness of Sherlock defending a killer, no matter how dense he sometimes was.

Sherlock was focusing almost all his attention on the letter in John's hand. He needed to read it, but he couldn't seem too enthusiastic about it.

"Well, give it to me," he drawled, extending his hand towards John.

"Oh, right, forgot I was holding it," said John absently, handing it over. He looked at Sherlock expectantly, as if expecting him to read it aloud.

Sherlock couldn't risk that. He didn't know what reaction he'd have to what was in this letter. So, not so much unlike how he always was, he turned on his heel and left without a word, going into his room and shutting the door.

On the outside was Sherlock's own name printed in Times New Roman. Generic ink, generic paper, could be bought anywhere. Told him nothing. In the privacy of his room, it made him grin—but he imagined it looked more like a wolf bearing his teeth.

Sherlock opened the letter up, folded just once down the center. He'd check it for skin or hair later—even though there was really no point. All that would be there was the skin from when John himself had picked it up—he should have known better than to pick something up like that, but maybe he knew as well as Sherlock that there was no point.

_Sherlock. It's been a very long time that you and I have been aware of one another, but it occurs to me that we've never talked. That seemed wrong, somehow. _

_Hopefully there are no hard feelings about my intimidating your boyfriend. I somehow thought it would make the best splash to put the letter in dear John's room. I thought it might catch your attention. And it did, didn't it?_

_I could have left it in your room, I suppose. But that's what you want, isn't it? Me to be in your room while you sleep. And I'm not sure I can give you what you want, not yet. _

_I'd like to hear from you, Sherlock. Tell me about me. I'd like to know what you've found out. _

_Though I think I know the answer._

_I hope I'm driving you mad. I really do. Only because if you're being driven out of your mind, that means you are thinking of me, and I like the thought of me being on your mind. _

_Also, I was hoping, Sherlock, that these correspondences could stay between you and me. If you don't terribly mind. _

_All the best:_

_The Surgeon_

Sherlock's mouth had gone dry—and admittedly, his trousers had gone tight. He knew. He knew how Sherlock felt.

And he was encouraging it. Well, mostly. He said he didn't want to give Sherlock what he wanted… but he'd said 'yet'.

The Surgeon. That was what he was calling himself. It was nice to at least have a name to call him other than 'the killer'.

Sherlock remembered the letter the first time he read it, but he still read it over and over again, for no particular reason.

His eyes flashed up momentarily when he heard John padding downstairs, but then Sherlock heard the sound of him taking his jacket and putting it on. "Off to work, Sherlock!" he called as he went out the door.

Good. Sherlock would be on his own for a while. He had to figure out how to respond.

He already knew he would fulfill the Surgeon's request in not telling anyone about the letter he was obviously going to send back. Sure, he would be able to think of an excuse as to why it would help the case—honestly, it just might, if this man would bother to make one single mistake by revealing just a little too much in one of the letters. The issue with telling them about the communications was that then Lestrade—or, god forbid, _John_—might want to see the letters. In fact, it was likely. And no matter how much Sherlock refused, Lestrade would eventually pull something about withholding evidence and then he would have to hand them over—or more likely Lestrade would take them by force when Sherlock _still_ refused even at the threat of arrest—and then none of them would be dense enough not to see.

Sherlock imagined the look on Sally Donovan's face if she knew that Sherlock was this intrigued with a murderer. Even after everything, she was still doubtful Sherlock's intentions could ever be trusted.

It made his lip curl to think she might actually have been right about him all along, when Sherlock himself had hardly even known.

Sherlock ignored all that. This whole thing with morals and caring was rather bothersome anyway. He did it for John, mostly. He focused his attention on the letter again.

How to respond? Cryptically, of course. Not giving away his sensibilities—this was why he didn't used to have friends, because then he didn't have any sensibilities to give away. What a hassle.

He needed to seem indifferent as well. No matter how much of a filthy lie it would be, it wouldn't do to clue the Surgeon in on how utterly fascinated Sherlock was with him so early on.

So. He had to begin sometime.

He decided to just handwrite it, since the man obviously knew who Sherlock was and wouldn't learn very much more based on his handwriting. It was easier to know that nobody else would see it if it was handwritten. He didn't like the idea of it ever being on a computer, where it wouldn't be truly gone even if the document was deleted. Plus, Sherlock's life wasn't very private anymore. Searching him online yielded infinite results—even if some of them weren't quite the truth, someone as clever as the Surgeon would be able to tell fiction from fact.

After rewriting his response fifteen times, burning them all when deemed inadequate, he came up with something he felt he could send. Just blasé enough, just vague enough. Well, it would do, at least.

_The Surgeon. Are you under the impression I would find that cute or something? But yes, it has been rather a while that we've been dancing around each other. I figure it seems only logical that we finally talk (in a manner of speaking) to one another. _

_You will find that John Watson is not actually very easy to scare. I wouldn't pretend to worry on him too much if I were you. Though I honestly see no point in putting it in that room as opposed to any other. And what is this about me wanting you in my room? I won't pretend I don't understand what you are implying, but I certainly don't understand why you're implying it. I also am rather amused by your sentimentality, if not puzzled. What special interest would you have in me? I am merely a detective following clues. If anything, I should think you would not be fond of me. _

_Yes, you know the answer of how much I know about you. Feel free to rub it in some more. You sending me letters can only help me in this respect, so laugh on, Surgeon. _

_Regards,_

_SH_

Sherlock finally decided that it was the best he could think of when his blood seemed to be boiling and he headed up the steps to John's room, putting it on the desk. John had put up wood planks in the broken window. Sherlock had been so absorbed he hadn't even noticed the noise—but he _had_ noticed John leaving, even though that had been nearly silent. Sherlock was so attuned to John that not even the Surgeon could distract him enough to not hear him.

Guilt bubbled in Sherlock's stomach. John. Every time he got caught in thinking about this man he didn't even know that he wanted to fuck into next century, he got stopped dead with John's face in his head.

John didn't deserve this. There was this little part of Sherlock that wanted to be honest with him. John might hate him for it, but he deserved the dislike at this point. And then John could find someone else. He always did, after all. When Sherlock left, he found Mary. When Mary died… Well, John went right back to Sherlock, but if neither were available, John would manage.

And if Sherlock were honest, and John left him… what would Sherlock do? Sure, he and John had only been together a mere couple of months, but Sherlock hadn't been honestly 'available' for decades. The only reason it wasn't his entire life was because he went through a few months of sexual desire in adolescence before abandoning it for ages—until John came 'round it lit the fire once more. Now Sherlock was more than capable of feeling that hot twinging in his abdomen, the curling, all-encompassing need in his mind to _touch_…

Would Sherlock drop everything and find a murderer? If he did, would he be so involved in a world of darkness that he eventually joined in? Their joined intellect would be unstoppable. Nobody would ever catch them. They would re-sculpt the living to join the dead and the people who were too stupid to know what they were looking at would cower, but the smart ones—they would know. They would see the rotting flesh with no sign of the hand that ended it, the poetry of the missing organs, and they would know what it meant. That this wasn't mindless murder: this was art. A smoker without his bad lungs and a pancreatic cancer patient sans their pancreas. Sure, it seemed simple, but it was a message: a person is only as good as their weakest link. Take away that flaw and they should be something better. But without even their very worst trait, they'll just die. Humanity was useless and dull and so, so _weak_, but it couldn't be fixed either.

What was Sherlock doing trying to stop murderers anyway? Planet Earth was certainly happier with less vermin around to taint her. Men like Moriarty he was glad to stop, but this… It was beautiful. Sherlock felt like he understood for the first time in a very long time—

He opened his eyes and found he was breathing very hard indeed. He was sitting in the front room. He didn't remember when that happened. He was sweating. And… and John was there. God, how long had he been like this? John was leaning in front of him, concern turning to relief.

"_Sherlock_." It was something like a pleased sigh. He smiled. "You were scaring me. What's the matter? Seen another hound, have you?"

Sherlock managed to smirk at the joke. "Just a nightmare, John," he replied easily.

"Oh. Wasn't sure you were sleeping, with the way you were sit—wait, you dream? You told me once you didn't."

"John, all people dream. I just tell you things sometimes to sound mysterious."

"Like turning up your coat collar?" he asked seriously, but with a light in his eyes that showed clearly he was making fun of Sherlock.

"Yes, and like wearing disgusting oatmeal jumpers in a sad attempt to try to hide how sexy you are. We all do silly things, John."

John had gone all pink, which had Sherlock genuinely grinning.

What had he been thinking? Let murderers get away with what they do? What if they ended someone like John? Not that anyone was truly like John, but someone else on this stupid planet had to be worth-while and Sherlock had to do what he could to stop someone like that from being killed.

And even if that weren't true, solving crimes was just too much fun.

Sherlock took John's neck and pulled him into a kiss, John's arms sliding around Sherlock's neck as he sighed contentedly into his detective's lips.

Sherlock really was going mad if he would give up John for anything in the world, let alone a murderer. And Sherlock was far too selfish to be honest with John and he knew it.

And Sherlock pointedly ignored the place in his mind palace, something like a file cabinet, where he kept the dark thoughts that he couldn't quite convince himself weren't the truth.


	3. Chapter 3

Sherlock quickly had to find a new place to exchange letters with the Surgeon. He explained in only his second letter that it was too hard to hide the letters from John—which was, he reminded the Surgeon, what _he_ had wanted—when they were in John's own room. They now were in Sherlock's coat pocket. Which seemed a strange place, since Sherlock wore his coat often, but Sherlock took his coat off each night and hung it by John's own jacket, and when Sherlock put his coat on once more, he'd feel in the pocket and there a new note would be.

Now there were no signs of breaking and entering, so it reinforced the idea that he had intended to be noticed the first time.

The letters weren't much like letters anymore after the first. They were sometimes very short responses, not trying to talk about as many subjects at once, without any salutations. The Surgeon's were typed and Sherlock's were hand written. They went as such:

Surgeon: _Sherlock, you will find that I know you far better than you might think. I know what you think of the crimes that I do. In a way, it was in part done to impress you. I knew it would._

Sherlock: _Be careful, you are starting to sound a little like an old rival of mine. You know him, I'm sure._

Surgeon: _I certainly knew him, yes. Do I sound like him? I'd rather not cause that comparison to be made. What am I doing wrong?_

Sherlock: _Taking special interest in me when I don't even know you, for one._

Surgeon: _Many people take interest in you, Sherlock. You have many fans now, thanks to your John—whom also has a particular interest in you, mind you._

Sherlock: _John knows me. I know John. That's different._

Surgeon: _Does he know you? Do you know him? When you hide so much from him, does it ever frighten you that he might hide things from you as well? Then again, I doubt he's clever enough for that. And I thought I might cause you a moment of self-doubt, too._

Sherlock: _Why is it that we exchange letters when they're so short? My phone number is on the site. You could just as easily text me._

Surgeon: _Changing the subject? It seems I accidentally hit a sore spot. What would dear John hide from you? Or is it just that you are so very guilty for hiding things from him?_

Sherlock: _Here's my mobile number, in case you can't get hold of a computer at the moment._

That was when the Surgeon finally obliged and they traded to text messages, which made correspondence much quicker.

The first text:

Surgeon: _You are persistent. Though I suppose I figured as much since you've been on this case about seventeen months and, even with nothing, you continue your search. Then again, you aren't doing it for noble reasons, are you?_

Sherlock: _There you go, thinking I have some sort of special liking for you or something. Have you yet considered that you might just be arrogant?_

Surgeon: _Sherlock, I know where you live. I know what you do when dear John isn't around to see. You may be able to trick everyone else in the world, but in the end, I'm the one who knows you._

Sherlock: _You're sounding like Moriarty again._

Surgeon: _Well the difference is that it's true when I say it._

Sherlock: _You think watching me means you know me?_

Surgeon: _You know better than anyone what a bit of observation can yield._

Much of it was like this. Sherlock couldn't be sure, but he thought this was the Surgeon's form of flirting. It wasn't really his area, and he couldn't well ask John, so he could only guess.

Sherlock spends more time fantasising about The Surgeon than actually trying to solve his cases at this point. He's not sure whether or not it matters.

He's zoning out again when he hears John say his name.

"What?" asked Sherlock absently.

John blinked at him for a moment. "Okay, Sherlock, what is it with you lately? Even when you aren't listening, you can relay everything I just said if you want to."

Sherlock thought back to a moment ago, but all he came up with was a tall, dark shadow of a person sneaking in through his window, Sherlock waiting with his breath held for the intruder to make his way over—

"It's hardly my fault if what you said is so unimportant I didn't even bother to catalogue it."

John glared for a moment. "Charming, as always, Sherlock. Maybe I'll just go to Sarah's."

That was always what got Sherlock to stop being a prat and John knew it. Sherlock was insanely jealous when it came to the ex-girlfriends—which was hardly fair, considering everything, but Sherlock never once claimed he was fair.

"Oh, don't do _that_," Sherlock muttered. "I was just starting to fall asleep is all."

It was the best excuse he could think of, and it was enough for John to sigh. "You do need the sleep. You've been up a lot lately." Another silence. "Is it because that killer struck again?"

"The Surgeon," said Sherlock before he could stop himself.

"What, you gave him a nickname?"

"He gave himself a nickname. Letter, remember?"

"Oh. Forgot about that, actually. You never let me see it."

"Too late. I burned it."

John snorted out something between a laugh and an exasperated sigh. "Should I even _ask_ why you thought that was necessary?"

Sherlock ignored that and began to muse aloud—this time in the way he was supposed to, about _catching_ the killer, not fucking him. "Rather boring this time. Just a man whose metal knee-cap was removed."

John looked disgusted for a moment. "Would you mind not talking about people dying like it's a telly programme for once?"

"I'm only saying The Surgeon seems to think he's rather clever with who he kills, but this time… just dull."

"Well the guy _had_ been in the papers."

Sherlock blinked. "He had?"

John sighed. "Sherlock, I swear, you're the stupidest genius who ever lived. The news is a good thing to pay attention to when you solve crimes for a living. Seeing as crimes can be found, you know, in the papers."

Sherlock ignored the whole rant, just saying, "Why was he in there?"

"He got in trouble for something," John said. "Domestic violence or something? Can't remember why it was such big news…"

Sherlock groaned and got up, going over to John's laptop. He opened it up, typed in the password, John complained about him guessing it again, he looked up the man…

Well, it was a bit more than domestic violence. He had been imprisoning his wife and daughter in the basement when everyone else thought they had been dead for ten years. Rather gruesome.

Sherlock then had a thought.

There was no way he could have missed this.

But had he?

He started looking up the past victims, seeing if they could be found in the papers too. No, not that. But criminal records?

There it was. The connection he'd never made. God, he really wasn't paying as much attention as he should have been, was he? They weren't all the same calibre of crime, but all criminals nonetheless.

Oh no. He was a vigilante. How dull! Sherlock found himself appalled at this new discovery.

And just then, an instant messenger popped up.

Unknown: _So you figured me out._

Sherlock's stomach still lurched, even with the disappointment coiling in his stomach. But he couldn't message the man so obviously. He glanced over to John. He was in the kitchen, grabbing a kettle. So not paying attention, in other words. Sherlock turned back to the computer.

Sherlock: _Here? Really?_

Unknown: _He won't notice. Delete the messages and he'll never look into it. You know that._

Sherlock sighed, knowing it was true. So he replied:

Sherlock:_ I don't know why I figured you were interesting._

Unknown: _The fact that I do not kill needlessly makes me uninteresting to you? I should think you more than anyone thinks doing anything without point is useless._

Sherlock: _No. You're just no different than any of the other killers I've caught. They all pity themselves too._

Unknown: _Pity myself? Dear Sherlock, that's not what this is at all._

Sherlock: _Fine, then revenge?_

Unknown: _Now you're the one being dull._

Sherlock: _Then what?_

Unknown: _Because I like to watch the life leave people, Sherlock. The light going from their eyes is something like art to me. And when the people you kill happen to be criminals… people put in less effort to catch you._

Sherlock's breath caught. Yes. _Yes_. Maybe he wasn't boring after all.

The Surgeon thought faster than Sherlock could respond this time.

Unknown: _Have you ever seen someone die, Sherlock? Have you ever seen the moment when it happens?_

Sherlock gaped at the message, not knowing what to say. After all his time around death, no, he hadn't. He thought he had, with Moriarty on St Barts, but he hadn't actually died, of course. But Sherlock had been too shocked to possibly savour it.

Savour… someone dying? What was Sherlock thinking? Sherlock felt a thin sheen of sweat on his brow, and he was just staring at the screen.

"Sherlock?"

He jumped and looked up. John was standing an arm's length away.

"What?" he snapped.

John looked concerned, but only said, "I was asking if you wanted a cuppa, but you were ignoring me…"

"Yes, I'd like one," he replied.

"What are you doing, anyway?" John asked.

"On your computer, obviously."

John rolled his eyes and turned away. "You're mad, Sherlock, you know that?" he asked as he was walking back to the kitchen.

Sherlock didn't respond, because another message appeared.

Unknown: _You never know if you're on the right side of anything unless you've tried both sides._

Sherlock: _Are you telling me I should kill someone?_

In Sherlock's head, the sentence didn't sound as vehement as it should have. If he were saying it aloud, he would have sounded breathless.

Unknown:_ I'm telling you that you don't seem the type for ignorance, and there's an entire half of your craft that you don't truly understand. In theory, yes, but with no sort of intimacy. And Sherlock, there is nothing more intimate than being someone else's last moment._

Sherlock couldn't breathe. He didn't know what to respond. And then he couldn't respond at all.

_Unknown has signed off._


	4. Chapter 4

"Please."

It was a whimper like none Sherlock had ever heard before. And he'd heard all sorts of desperation in his life, some that made even his cold heart cringe... but this was a whole new level. This was primal terror, but also complete hopelessness. This person, this utter stranger that Sherlock had never seen before in his life, could see in Sherlock's eyes that there was no hope. The pleading was empty. He knew it wouldn't save him, but he couldn't help but cling to his rapidly ending life as hard as he was able.

Sherlock hadn't meant to take it this far, not really. He just got a knife and was going to stab someone, make it look like an ordinary mugging. Just as an experiment. The person was dying of lung cancer anyway, so Sherlock wasn't doing much harm.

But then Sherlock found the man, and he knocked him out. And he dragged him to an abandoned warehouse. And he put the man on his side, and he took the knife like it was some sort of scalpel and made an incision between two ribs.

The Surgeon used a paralytic on his victims, so they couldn't move and ruin the procedure, but they could feel it.

Before Sherlock did the same, the man gave the one whimper. The pleading one even though he knew it was useless. Sherlock might have smiled in response.

He didn't have the tools he needed and he knew it. Going online wasn't truly enough to know how to perform a pneumonectomy.

So he didn't. He took the knife and made several more cuts, enough to rip the skin back, to reveal the tissue underneath.

It was different when it was alive. When the lungs were still working, if not rather haphazardly. Sherlock wasn't being careful the way The Surgeon was. This man would die of shock at the amount of pain he was about to feel. Sherlock didn't care. He just needed to know.

He didn't remember grabbing the hammer, or when he decided he was really going to do this.

He brought it down on the man.

_Crack. _

Sherlock grinned.

_Crrrack_.

The man couldn't move, not even to grunt.

Sherlock broke each one. Then he put his fingers in the chest… and he heaved. More cracking, one rib was out of his way. Then another. Sherlock didn't know if the man was dead yet. He didn't register anything, not the splatter of blood on his own face, not the slinters of bone being left inside the open side. He just had to get to it.

He tore past all the other flesh until lung was visible. He wasn't enough in control of himself to decide if the man would have really needed a pneumonectomy, or if a lobectomy would have sufficed. None of that mattered. He took his fist around the lung and he tore. It came free more easily than he thought it would. How fragile a human body was.

Sherlock was breathing too hard, as if to compensate for the man who had stopped. His eyes were wide open, unbearable pain his very last sensation.

Oh, pity. Sherlock hadn't watched the life leave his eyes.

Well. He'd just have to try again sometime.

* * *

Sherlock shot up, breathing so hard it sounded more like sobs. Maybe it _was_ sobs.

It'd felt real. So real. Now that Sherlock was awake, the whole thing was implausible, from not getting caught in the middle of what he was doing, to the paralytic he magically had on his person, to how uncomplicated it had been to disassemble a body when it would surely take more effort than that. But none of that mattered because Sherlock had been sure it was really him. He was surprised when he lifted up his hands and there was no blood dripping down to his elbows. The thought made him want to vomit.

"Sherlock!" John gasped, taking Sherlock in his arms. "It's okay, only a nightmare," he said.

Sherlock let John hold him, not knowing what to think of what had just happened.

His imagination going wild with him, obviously. He'd never really feel that way if he were doing that to a human being. He couldn't.

"I—need to—toilet," Sherlock said in a sad attempt at the English language, but John just nodded and let Sherlock go.

Sherlock didn't notice the stickiness between his legs until he started walking, but didn't dare look down at it until he had safely locked the door.

He looked in the mirror and sure enough, for the first time since he was fifteen, he'd experienced what they call a wet dream.

Sherlock's breath caught.

This was getting out of hand. He had a dream about—about—

Pictures of it flashed in his mind. The sound of his hands as he rummaged through a chest cavity. The dead, petrified eyes in the man's head.

_He likes it. He gets off on it. _

He hadn't heard Donovan say the words, but John had told him about the conversation.

His pride flared. No. She was _wrong_. The Surgeon was wrong too.

He looked down at the mess his pyjama trousers were… and saw that his hand had inched into his pants at his musings.

Sherlock never had the moral compass that other people did, never had the one he should, but he was enough of a human being to feel how utterly wrong all of this was. What _was_ he?

_There is nothing more intimate than being someone else's last moment._

"Shut up," Sherlock said aloud at the memory.

He didn't realise when he'd slid to the ground, his hands over his ears like he was being whispered to, but all he wanted was not to hear it.

His hard breathing was irregular again. He vaguely realised it really was sobbing this time.

No. This wasn't who he was.

He heard the words in his head like The Surgeon was right there in the room with him.

_No, not who you _were_. But who you were and who you _are_, those are two very different things. You have no idea how a person can change, Sherlock. Well, you _had_ no idea. Now you're starting to see it. _

"Shut _up_!"

_No. I'll never shut up again and you know it._

Sherlock whimpered, and if it had made a word, it might have been 'please'. And it wasn't so different from the man in his dream. Pleading even when there's no point, when your own fate is out of your hands entirely.


	5. Chapter 5

When John's body was limp, pale, and cold on the floor in the middle of the flat, Sherlock was sure he was asleep again. He'd been having countless nightmares lately. It was another, that's all. He'd gotten to the point that he could wake himself up from said dreams by causing himself pain. Because of this, he didn't panic. He just went to the kitchen, grabbed a knife, and slit his hand.

He hissed and dropped the knife in surprise at the fact that there was sensation. The cut dripped steadily onto the floor for the five seconds it took him to comprehend what this meant.

"John," he breathed, stumbling over to the body.

The Surgeon had made a mistake this time. If he killed John, Sherlock would stop at nothing to find him and _end_ him.

He fell on top of the body, already numb with the thought of living without John. He couldn't. He—

In a moment of madness, he called John's mobile.

It went to voicemail after a few rings.

No. No no no…

Sherlock had entertained this. In not looking for The Surgeon the way he should have, he allowed this to happen. This was his fault, and he would never, ever forgive—

His phone rang.

John.

Hope blossomed in Sherlock's chest and he answered the phone on the first ring.

"John?" he asked.

"Who else would it be?" he asked, not completely unkindly, more teasingly.

He sighed a shaky breath of relief, and then looked down at the body in front of him. This was not John, he saw the moment he got a close look. There was a mask—rather expertly created and placed, mind you—on him, but it was the shape of the body that made Sherlock sure. Well, and the fact that John's voice was there in his ear.

"Sherlock?" John asked, sounding concerned.

"You—I—"

There was a silence. "Another nightmare?" asked John gently.

Sherlock didn't know how explain his strange midday ring otherwise, so he muttered, "Yes."

"I've technically got nothing else on today," John said. "Would you like me to come home?"

"Yes," said Sherlock again weakly, and nothing Sherlock ever said was more true.

"Okay," John replied, a smile in his voice. "See you soon."

The line went dead. Sherlock looked back down at the body, the prosthetic mask that looked far too much like his John.

Then he saw it. The note sticking out of his pocket. His hands were shaking when he took it out and unfolded it.

_Make your choice, Sherlock._

What, choose between a murderer and John? Why was that a question? It wasn't. There was no way it was.

Text message now too.

Surgeon: _It's not me and John you're choosing between, Sherlock. It's a life in the light or in the dark._

Sherlock scoffed aloud.

Sherlock: _If you're saying I lose John by going your way, you should know my answer._

Surgeon: _I'm saying you're going to lose him either way._

Sherlock grit his teeth.

Sherlock: _Are you threatening him?_

Surgeon: _No, actually. I am only saying that no matter what you choose now, the curiosity has already set in, and we both know how addictive your personality is. It's only a matter of time before you choose._

Sherlock: _What, you think I would hurt John, no matter how far I fell?_

Surgeon: _Never intentionally, of course not._

Sherlock: _Fuck you._

Surgeon: _Ooh, touchy. I love striking a nerve. Well, on that note, all in due time, Sherlock._

Even with how disgusted he was feeling in that moment, the text message made his guts clench, his eyes shut in a strange, murky, erotic scene Sherlock could just barely see, and the mystery was what made it so impossible to ignore.

Sherlock's eyes flashed open. Had to dispose of this body before John got home. That was what was important now.

He made quick work of it, because the world really was lucky he'd stayed (mostly) in the light all this time, because Sherlock would make a _very_ good killer indeed. He knew where to hide it so that nobody ever saw it again.

Only then did Sherlock feel in control of himself enough to send another message. It was a complete change of subject, and Sherlock wasn't absolutely sure why he said it.

Sherlock: _I have killed someone before, you know._

Surgeon: _You refer to Charles Augustus Magnussen._

Sherlock: _Yes. And I haven't gone on any killing sprees since. Wouldn't that have unlocked my addiction, if I were in fact ever going to have one?_

Surgeon: _You know as well as I that the person dying isn't the part that matters to me, that would matter to you. It's before that. A gunshot hardly counts as a murder. There's no passion in it._

Sherlock swallowed. More things he didn't want to think about too hard. He changed the subject again.

Sherlock: _Why don't we talk about you some more?_

Surgeon: _Me? What would you like to know?_

Sherlock: _Have you always killed people, since you were young?_

Surgeon: _No._

Sherlock: _You say you don't do it because of any sort of self-pity or revenge… but did it start that way? You must have killed the first time for a reason._

Surgeon: _The very first time was a drunken accident. Alcohol assuaged my emotional problems, not blood. And now I don't feel all that much of anything. It's quite pleasant, really. Only for you._

Sherlock: _For me? Why?_

Surgeon: _Because you are the only one with the potential to keep up with me. With you by my side, we could do anything. Everything._

Sherlock: _Is that what you want? Me to run away with you?_

Surgeon: _It's only a matter of time, Sherlock._

"Sherlock! I'm home!"

Sherlock jumped at the sound of John at the bottom of the stairs.

Sherlock: _In your dreams._

John came through the door, hung up his coat.

"You're eating today whether you like it or not," said John as he headed for the kitchen.

His phone buzzed.

Surgeon: _Or yours. _

Sherlock couldn't bring himself to reply to that one. He didn't end up having to.

Surgeon: _What life do you want, Sherlock? Be honest with yourself._

"So what do you want?" John asked from the kitchen.

"I don't know," Sherlock muttered. He didn't know who he was replying to anymore. He didn't know anything anymore.


	6. Chapter 6

"Mmmm, _Sherlock,"_ John murmured lovingly into Sherlock's ear, planting a kiss behind it. He was still breathing hard, and his body was covered in a sheen of sweat.

"Yes, I quite agree," Sherlock replied absently, staring at the wall. There was no passion in his voice. There wasn't much passion in anything anymore.

John sighed. "I wish you would tell me what's wrong. It's been too long since you talked to me."

"I talk to you frequently."

"And suddenly it's all about me. Did you think I wouldn't notice a total narcissist suddenly saying nothing about himself?" John meant it as a joke, but Sherlock didn't smile. John sighed again. "Sherlock. Please."

"There's nothing to tell."

"You're always saying that now."

"Because it's true."

John grunted, frustrated now. He pulled away from Sherlock's back, standing. "I'm getting a cuppa."

And he was gone.

Sherlock couldn't even bring himself to care that he'd upset John again. He was doing that a lot lately.

_I'm saying you're going to lose him either way._

He was starting to understand that now. It didn't matter that Sherlock was ignoring all his curiosities that The Surgeon had put in him. It didn't matter that he no longer responded to the texts. His mind was caught up in The Surgeon's world. Where he could be apart from everyone, but still show off his brilliance. He was addicted to the idea of it, like The Surgeon knew he would be. It was always there, nagging at the back of his mind, and it caused him to care very little about everything else in his life.

Even John. He knew that, somewhere inside him, that love for John was still there. But it was being smothered. Choked into submission so it could be tied up and ignored.

Interesting choice of description. Sherlock wasn't stupid enough to think it was a coincidence.

He'd gotten another text earlier today. He didn't check his phone much anymore, since there was always a text waiting.

He picked it up and gave it a glance.

The Surgeon: _Tonight, I'll be at the location where you found Alex Woodbridge._

Sherlock sat up quickly, staring at the message. His mouth opened, and then closed again.

Sherlock: _You're telling me where you'll be? Don't you think that's a little risky?_

The Surgeon: _Not in the slightest. I shall see you tonight. Don't ruin the fun by bringing any friends._

Sherlock's breath caught in his throat. _Oh_. This wasn't some strange version of him turning himself in. This was him wanting Sherlock to meet him there.

Why today? Why did he trust Sherlock today not to just tell the Yard about it?

But then again… what reason was there _not_ to go? Sherlock was increasingly unhappy with his own life. This fantasy was the reason why. If it turns out the way he wants it to, then he leaves. If it's nothing close to what he wanted, he contacts Lestrade and The Surgeon goes to jail.

There wasn't anything to lose.

No. _No_!

What in hell was he thinking? He was going mad if he thought that made any sense. He couldn't know what would be waiting there for him. He might not have a choice once he's there.

He stood up, threw a dressing gown over his naked body, and went out into the front room, where John was drinking his tea and brooding. He'd gone upstairs and dressed, which meant Sherlock had been in the room longer than he thought. Still upset with Sherlock, obviously.

"Well, you're walking around," John said. "_That's_ something." Then he looked at Sherlock's panicked face. "Please tell me what's the matter. I just want to help."

"Well I don't want your help, so just stop asking!" Sherlock snapped.

John looked taken aback. "You stopped doing this to me a long time ago, Sherlock. Keeping me out. Why are we back to this again?"

"Because maybe I don't want you in my every thought, alright?"

Sherlock didn't really mean it. He was just confused and didn't know what else to say to get John to shut up. Hurting him to get him to be quiet was a strategy he hadn't employed in a long time, but John wasn't stupid. He surely remembered when it was a frequent occurrence.

"I'm starting to wonder if you want me in your life at all anymore," John replied.

Sherlock looked over to him sharply. "Don't be daft."

"But that's just it. All I am to you is stupid or daft or dense anymore. That's how it was back in the beginning, sure, but I thought we had gotten past all that. And I don't want to go back to that. So you're going to have to choose, Sherlock."

Yes. Yes, everything in his life was about choosing right now. "Choose what?"

"Between me and apathy. Because I can't sit around and watch you be like this. It hurts me."

"Maybe this is just who I am," Sherlock replied. "Maybe there's nothing either of us can do about it and we were just pretending I could be more."

John wouldn't have looked more aghast if Sherlock had slapped him across the face.

John rubbed his face. "I need some air," he said. "If that's your answer, I need a _lot_ of air."

He went over to get his coat. Sherlock always stopped him before he got out the door when this happened now. It had been a long time since he really let John storm out. Even in his mood lately, he always stopped him.

But this time, he let him go.

In a sort of trance, he went to his room, dressed, and packed some clothes. He hardly knew what he'd need, but he tried. He considered leaving a note, but that wouldn't help anything for John, would it?

He still considered that if he came to his senses, he could possibly turn The Surgeon in. There was still that chance.

But right now, he didn't know where his senses were. Because he didn't want this. He didn't want to be this unfeeling thing while John just watched in horror on the sidelines. It wasn't fair to him. If Sherlock was being selfless for the first time in his life, that would be his reason.

But he wasn't, of course. He just needed to know. It had been running through him like a disease and he just had to _know_.

So he went out the door too, and looked at 221 from the outside.

Possibly for the last time.


	7. Chapter 7

Sherlock took a cab to the shore of the Thames where he and John once examined a museum guard who had been killed by the assassin The Golem.

Melodramatic names for killers seemed to be a significant part of Sherlock's life right now.

He still was unsure what he was actually feeling at the moment. About anything. The thought of leaving John behind left him strangely numb.

And he still hadn't called Scotland Yard. He knew he wouldn't though. He wasn't so numb that he was unaware of his own intentions.

What would he find when he met The Surgeon? Could all of his wild fantasies be anything like the truth?

Well, he was soon to find out.

He got out and paid the cabbie far too much. It didn't matter to him now.

He walked down to the waterline and saw a figure in the distance.

There he was. Like he said he would be. And seemingly alone, at that.

He hadn't noticed Sherlock yet. He could still call the Yard and just get this psychopath arrested. It would be easy.

He didn't even reach for his mobile.

He took a few steps. A few more.

He was a little surprised that the man that was obviously a genius hadn't noticed him yet. He wasn't sneaking, after all. Maybe his perceptions weren't so impressive in person.

Maybe he in general wasn't as impressive as Sherlock had always figured.

Could whoever this was really stand up against John? John, the one who always understood him? The only one who had accepted him for everything that he was?

Was Sherlock making a mistake?

That was when the man seemed to notice him. He turned—

Sherlock blinked. And did it again. And a third time.

His first thought, his very first, was that he couldn't believe this was happening again. The pool. Where Sherlock had been expecting a killer and saw John instead. And then realized a bomb was strapped to him, but for half a moment, he thought John really was the killer.

But this time, he made the assumptions in the opposite order. Oh, The Surgeon took John. Original.

But then he looked at John's face. Even in the gathering dark, he didn't look particularly frightened. Or upset. Maybe he looked a little smug.

"John?" Sherlock managed to choke out.

John stepped forward. "I really wondered if you had figured me out, and you were just humouring me. But from the look on your face, I was wrong there."

Sherlock didn't know what to think—maybe for the first time in his life.

Sherlock, suddenly, had a very late deduction. He remembered every time he got a text from The Surgeon, John was either not in the room or had been on his phone only moments before.

John was the one who found the note in his own bedroom.

John's DNA being the only thing he could find after the break-in.

John was a doctor, the only doctor in the UK Sherlock hadn't looked into as a suspect.

John…

Before Sherlock could think of a single thing to say, John was speaking.

"I'm sorry about how much this has all put you through. You're so stubborn, I didn't see any other way."

Sherlock didn't hear it, not really. He was still trying to think straight. To understand.

"How?" Sherlock finally asked.

Part of Sherlock was embarrassed. He adored John, but John was no genius. How did Sherlock not manage to figure John's plan out when he was 1) pretty ordinary and 2) _living in his flat_?

John stepped towards Sherlock. "Who in the world knows you better than me? Who has seen your methods over and over and knows exactly what you look for? And so, who's the most likely to be able to trick you?"

Sherlock's mouth was flopping open and closed wordlessly.

"The ideas were mine, but I copied some of them. Anything that confused you in other cases, I did myself. And then I started the letters when I was afraid you were going to figure me out to distract you. I'm sorry to say, I'm no genius. I just know you, Sherlock. Better than you know yourself, sometimes. So anything I couldn't do myself, I paid someone to do for me. The funny thing is, I only was trying to fool you. You're the only one I know _how_ to fool. If the Yard had a little less faith in you and looked into it themselves, with a different eye, they might have seen it. But they didn't, because they had you and knew that had to be better."

But the most important part of this whole thing was only just dawning on Sherlock.

This means that his virtuous, kind-hearted John… killed people.

And liked it.

John had killed before, but Sherlock had known his hesitation at ending a life. What had happened?

"How could you do it? Was this all to get my attention?"

John rolled his eyes, but had a kind of fond smile on his lips. "It's not all about you _all_ the time, Sherlock. No, it wasn't about that, not at first. It was… I was mad. At everything in the world. I lost Mary and my baby and I hated everything for it. The first killing was an accident. That was true. And the feeling of it…. I liked it. I never thought I would, but I did. I found something that I'm inexplicably good at. And I like to think that killing those people did some other people some good. Even if some of them had only been wronging a single person, I saved them." John was quiet, watching Sherlock continue to flail. "Is The Surgeon boring now that you know he was me?"

"But…" Sherlock was able to mutter. "You didn't talk like you," he added lamely.

"It's not so hard to put on a character. Especially when it was only writing. I thought pretty hard about the way I phrased things. I had to stretch the truth once or twice, just so I didn't lose your attention."

Sherlock still couldn't believe this. He'd never been so confused before. John… _John_…

"Sherlock," John said, stepping forward again. He was close now. Too close. Not close enough? Sherlock didn't even know anymore. _"Sherlock,"_ John said again, and that's what made him meet John's eyes. Because it was that same voice. The voice John had when Sherlock—as rare an occasion as it was—was too bewildered to function. Or was feeling—also rare—insecure. That same loving, forgiving voice Sherlock had always adored from the start.

"So you started killing people," Sherlock whispered, "And all you needed to be infallible was me."

John smiled a warm smile. How could he still be warm, after all he'd done? After he'd found the demon inside of him and let it take him over? How could he still be good?

"No, Sherlock. I haven't been caught yet. I didn't need your help. No offense," he added with a smirk. But then he was serious again. "I didn't need you to be the perfect killer. I needed you because I love you, you daft madman." John had never said it before. Neither of them had ever plucked up the courage. Not until now.

"But… all the games. Why didn't you just tell me?"

"I had to be sure you wouldn't just turn me in."

"I still could have. I thought about it."

"But you didn't. Our correspondences were enough for you to see that you love this side of me too. And I love the dark side of you, the same as the light." Sherlock was blinking down at John. _His_ John. "You always thought life in the light was dull. I know you did. So let's go."

"Where?"

"Anywhere."

"They'll know it's us if we vanish, won't they?" Sherlock asked.

"Come on, Sherlock. You know that isn't true. They'd never _want_ to believe it was us, so they wouldn't believe it. And even if they did," John added, "We'd never be found."

Sherlock didn't know what his face was revealing, but John was getting more confident. He closed the distance between them and pressed his body against Sherlock's. "It'll be just you and me and whatever we want to do. No more control, no more chains. Freedom, Sherlock. And we can purge this stupid world of all the idiots that taint it."

It's funny how the dark side of John sounded strangely like something deep inside of Sherlock.

And Sherlock realized then that he could think about it for years and there were some things that wouldn't change.

One, he had always lusted for this type of thing.

Two, after this, things couldn't go back to the way they were. It was either stay together or be apart.

Three, John was right. Sherlock loved him. Everything about him. This too. If anything, this made them more similar than they had ever been.

"Just you and me," Sherlock repeated.

John grinned, and got on his toes to kiss him. It was soft at first, but then it changed. It was primal, harsh.

Everything Sherlock had been wanting and it was always right in front of him.

"I love you," Sherlock breathed.

"I know. Are you ready?"

Sherlock was scared, he had to admit. Leaving everything he knew. Being in a situation where someone else actually knew more than he did—John had been at this a while now. He was the expert of something for once.

Sherlock took John's hand.

And for the first time, the smile that John gave in return wasn't kind. Too much teeth, with brows and eyes that hinted at something much darker than joy. It was just a little bit… evil.

And the strangest part was that Sherlock didn't mind.

"I'm ready," Sherlock replied. "But John... you killed _Moriarty._ That's... I didn't think it was possible. How..."

John smirked over at him. "Ah, yes, Jim." Sherlock was surprised with the familiarity there. "He was the twelfth. It's a funny story, actually. But we have plenty of time for that. All the time in the world."

And they made their way into the darkness.

* * *

**Thanks for reading. I hope you enjoyed. If you want horrible recounts of them murdering people, a detailed description of how exactly John killed Moriarty, or super kinky sex, I could make that happen, but I think this will do. **


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